COLONIA LEBARÓN, Mexico — When a 16-year-old boy was kidnapped from this fundamentalist Mormon community in early May, ransom was set at $1 million. The town chose not to pay.

Instead, led by the boy’s older brother, members of the community traveled to the state capital, Chihuahua, to demand that the government catch the kidnappers. Nobody knows exactly why, but seven days later, the boy was freed.

Soon, from other towns scattered in the valleys that stretch under the purple-rimmed mountains of the Sierra Madre, farmers facing extortion and intimidation began pleading with the crusading brother, Benjamín LeBarón — a great-grandson of the Mormon community’s founder — for help.

He tried, forming a group to help towns put pressure on the authorities. And then he was dead.

On July 7 at 1 a.m., four S.U.V.’s rumbled to the home he shared with his wife and five children. Armed men pried open the front door. Luis Widmar, his brother-in-law who lived nearby, burst in to try to help. But the gunmen took both men away. Their bodies were found later that day with a note accusing them of providing information leading to the arrests of gang members in a nearby town.

Two and a half years after the Mexican government started its war against drug cartels, the crackdown has, in some places, only made life more dangerous. Here in the northern state of Chihuahua, the threats, kidnappings and violence did not begin until last year, about the same time the government sent troops to Ciudad Juárez, which is a four-hour drive from Colonia LeBarón.

“The extortion began about a year ago,” said one Colonia LeBarón resident who left Mexico after Mr. LeBarón and Mr. Widmar were killed, and asked not to be identified out of fear for his life. “We think the narcos’ money is drying up and they are resorting to whatever they have to do.” People here say they believe that the military presence on the border has pushed gangs into the countryside.

The local police chief was killed in November. Armed men followed the mayor’s children and his wife as they went to school.

The town treasurer of another small Chihuahua town, Namiquipa, was killed last year. The police chief and a top commander have been missing since October. The mayor, who had been receiving death threats since last year, was killed July 14.

The drug war remains intense in Ciudad Juárez, where there have been more than 1,000 killings this year. Drug cartels are continuing their brazen displays of violence against Mexican authorities. A few days after Mr. LeBarón and Mr. Widmar’s funeral, 12 off-duty federal police officers in the western state of Michoacán were kidnapped, tortured and killed, their bodies dumped in a pile on a highway.

The government piled more troops into Michoacán, and on Thursday, the federal police announced the arrests of four men in the case. Ten municipal police officers were detained after the killings as authorities investigated whether they protected the killers.

Looking back, the signs of how great the risk Benjamín LeBarón and his group, SOS Chihuahua, were running seem obvious.

“People began to call us,” said the man who left the country. “They figured we could pressure the government on their behalf. We started to handle kidnapping and extortion cases.

“Then we felt we were going to begin to get into a dangerous situation. We were afraid that the family would be killed. But Benji said, ‘I feel their pain. I can’t let them down.’ ”

SOS Chihuahua had a manifesto that urged citizens to overcome fears of organized crime and to give tips to the authorities.

“Everybody is scared to give information to the government,” said one resident who worked with Mr. LeBarón. The call to start cooperating must have hit a nerve with the criminals, he said, and the group was “a threat to their impunity.”

The family asked for protection, and about a dozen state police officers in mid-May began training a community police force. Soldiers and state police made rounds through LeBarón and the nearby town of Galeana, where Mr. LeBarón lived. But there were few illusions.

“Any criminologist will tell you that when they want to get somebody, there is nothing that can be done,” said a state police investigator who asked not to be identified because he was not authorized to speak publicly. “You cannot put a police officer in front of every house.” Still, Colonia LeBarón had its own special history, and its people thought they had the wherewithal to stand up to fear.

The town was settled in the 1940s by Alma Dayer LeBarón, who had come to Chihuahua with other Mormon settlers but was excommunicated after he took a second wife. Polygamy is fading now, but many adults have dozens of siblings, and much of the town is related by marriage. Benjamín LeBarón was one of his father’s 51 children.

The people here favor English over Spanish and worship in a sand-colored, wooden church decorated with framed quotes from George Washington and Benjamin Franklin.

They have dual citizenship, and many work for years in the United States to earn money to buy land and build houses here. The village is surrounded by chile fields and pecan orchards.

But there is also a dark side. Benjamín LeBarón’s grandfather Joel, the son of Alma Dayer LeBarón and revered by many in the community as a prophet, was killed in 1972 by followers of his brother, Ervil, at a settlement the brothers had set up in Baja California. Ervil LeBarón’s cult continued its killing spree in the United States for more than 15 years.

Those who worked to help set up SOS Chihuahua do not know how they will carry it on. The town is terrified. There are no children playing on the lawns or riding their bikes along the gravel streets. The crunch of a coming truck provokes an anxious glance, but it’s just a neighbor.